NTC  Project: F04-AE01

Coated and Laminated Fabrics for Fuel Cells

 

Project Team:

Leader Sabit Adanur / Auburn Engineering / Fabric and membrane structures and technology

Email: sadanur@eng.auburn.edu Phone: 334 844-5497

Members:              Ben Choe / Auburn Mechanical Engineering  /choe@eng.auburn.edu/ fuel cell technology

                                Qinguo Fan / UMass Dartmouth / qfan@umassd.edu / textile chemistry and chemical analysis

                                Steve Warner  / UMass Dartmouth  / swarner@umassd.edu / material science, polymer structure

Objective:

                This project deals with the coating and laminating needs of membrane-based fuel cell components. The precise size and shape of the coated area is a concern in fuel cell manufacturing.  This research will characterize the fundamentals of coating and laminating the active components in fuel cells with the aim to increase efficiency, reduce cost and further develop and optimize the substrates, recipes and process technology.

Relevance to NTC Mission: 

                In his State of the Union address on January 28, 2003, the President urged the U.S. scientific community to develop fuel cells for hydrogen powered automobiles [1].  Although the concept of fuel cell is old, the interest in them has risen over the last 20 years with the need to find alternative energy sources [2,3].  Fuel cells are the ideal energy alternative in the near future; they require no recharging and they are pollution free, since the only chemical byproduct is water.  They are suitable for both stationary and mobile use.  Depending on the size, a fuel cell can generate enough electrical power to run a laptop computer, a small car or a city bus.  Fuel cells can also be used in utility generation.  Germany and Japan have been testing vehicles powered by fuel cells.  Coated and laminated textile materials are used as membranes in fuel cells. In fact, the membrane is one of the most critical elements of a fuel cell [4,5].  Therefore, the textile engineering community would help with the President’s initiative to design better fuel cells, which would open up new opportunities for the textile industry that are consistent with NTC goals [6].

State of the Art:                                  

                                               

                                                Figure 1  Schematic of a fuel cell (Ballard, Inc.)

                A fuel cell is a battery that produces heat and electricity via an electrochemical reaction.  It does not need recharging so long as hydrogen and oxygen fuel are supplied.  A fuel cell is constructed by sandwiching an electrolyte between an anode and a cathode.  The fuel, hydrogen, is fed to the anode continuously.  A catalyst activates the system; the hydrogen gas is separated into protons and electrons.  The electrons are conducted through a wire.  The potential difference between fuel and oxygen produces an electrical current.  The protons travel through a special proton exchange membrane and combine with oxygen to produce heat and water byproduct, the water being removed as water vapor [7-12].  Figure 1 is a schematic fuel cell.  Although the research on fuel cells has intensified within the last 20 years, the principle of a fuel cell was discovered in 1839 by British lawyer and amateur scientist, William Grove.  He used four large cells that contain hydrogen and oxygen to generate electric power [13].  In stark contract to servo motor power, fuel is converted to thermal and electrical energy directly, electrochemically, in a fuel cell.  Schematics of the two systems are shown below [14]:

 

Servo motor-power unit:

 

 

 

 

 

 


Fuel cell-power unit:

 

 

 

 

 


               

                Although there are several types of fuel cells, the polymer electrolyte membrane fuel cell (PEMFC) has especially high potential for future.  In this fuel cell, a polymer membrane acts as the electrolyte to transport electrons from anode to cathode.  This work focuses on the polymer electrolyte membrane (PEM) and gas diffusion layer.  The current membrane uses a fluorinized Teflon®-based polymer membrane such as Nafion 112-117 from DuPont.  The gas diffusion layer can be woven or nonwoven carbon, such as SGL or Lydall paper.  The current properties and future goals of the PEMs are given below [4,13,14]:

 

                Property                                 Present                                   Target

                Efficiency                              35%                                        40%

                Cost $/kW                             300-500                                   30-50

                Durability                              2000 hours                             5000 hours

                Operating temperature        80oC                                        -40 to 200o C

 

                Fuel cell stacks are made of 100-200 individual fuel cells. Each fuel cell contains a membrane electrode assembly (MEA).  The area of each membrane is approximately 25 cm2.  The membrane separates oxygen and hydrogen in the fuel cell, which should not be mixed; however, a certain amount of moisture in the membrane is necessary for the proton transport.  The membrane is 50-180 μm thick. 

Approach:

                Improving the membrane electrode assembly (MEA) structure and manufacturing is the subject of this work.  Dispersion of materials, coating and laminating are the key issues to be addressed. Fuel cell coating is an extremely complex process.  Fiber chemistry, surface texture, coating paste, application process and paste distribution all affect the properties and performance of the coated, laminated surface structure.  An array of process technologies are used: impregnation, coating, drying, cooling, sintering, calendaring, laminating and finishing [14,15].

 

Approach 1. Coat catalyst onto the gas diffusion layer

                 Step 1:   Impregnate, sinter, and cool. The carbon substrate will be impregnated with PTFE                                                                (Teflon®). A double sided coating system may be appropriate for this process.

                Step 2:    Coat on the carbon layers, dry, and cool. Impregnated material will be carbon-coated, resulting in                                     impregnated and coated material.

                Step 3:    Coat catalyst, dry, and cool. We will coat the anode and the cathode to obtain a gas diffusion                                           electrode (GDE) anode and a GDE cathode.

                Step 4:    Laminate and seal. This may be done continuously or discontinuously. The GDE anode and                                              GDE cathode will be laminated with Nafion™ or other membranes to obtain MEA and GDE.

 

Approach 2. Coating of the catalyst on the membrane

                Step 1.    Impregnate, sinter, and cool. Carbon substrate and PTFE will be impregnated.

                Step 2.    Apply carbon coat, dry and cool.

                Step 3.    Apply catalyst coating, dry and cool. Cathode base coating and anode base coating will be                                               combined with Nafion™ or other membranes to obtain MEA.

                Step 4.    Laminate and seal. Two gas diffusion layers (GDL) will be combined with MEA in the center.

 

                There are still many roadblocks for wide commercial applications of fuel cells: operating pressure and temperature, the cost of per kilowatt produced, and the need to have pure hydrogen.  Regarding the textile components, “PEM fuel cell researchers are looking for new polymer membranes to improve the performance and durability of their fuel cells. In order to operate properly, the membrane must remain humidified, which prohibits operation at higher temperatures.  However, there are benefits to operating at higher temperatures, such as resistance to catalyst poisoning and higher output current densities.  New membrane materials under development will stay humidified at higher temperatures, making fuel cells more likely to find use in vehicles and other applications.  Not only will they be less sensitive to catalyst poisoning, but also smaller fuel cell stacks will be required to get the same power output, thus lowering their cost” [16].

 

This Year’s Goal:

                The participation of textile engineering schools in fuel cell research has been minimal. Textile engineers and scientists to get involved with this important research area.  Current fuel cell technology will be analyzed in the first year in much more details, but here clearly is a need here.  The current fiber types, surface texture, coating formulations and processing will be studied.  The benefits of using new or different fibers and fabric structures will be investigated.  New polymers may be needed for membranes to improve the performance and durability of fuel cells.  Identifying new materials will be part of the first year’s goals.  A membrane in a fuel cell should allow proton transfer and prevent the transfer of hydrogen (fuel) and contaminants [5]. Surface characterization of the MEA will be done.  New possibilities will be explored to find the optimum membrane material and structure for most efficient proton transfer.

Outreach to Industry: 

                Manufacturers of fuel cells, fuel cell components and machine builders are interested in this work. The major companies in manufacturing of fuel cell components in the U.S. are 3M, W. L. Gore, and DuPont.  BC Technologies, Inc., of Spartanburg, SC, is interested in coating and laminating technology improvement and automation.  Close coordination is being established and will be maintained with the industry.

New Resources Required: 

                A lab scale, coating system is needed for this work. The Coatema EasyFuelCellCoater, which is a knife-over screen coating system, is appropriate for our application and is offered at a reasonable price. The equipment can apply catalyst solution and stack elements accurately and evenly [17, 18]. The catalyst can be applied to either a carbon or a membrane layer. The cost of the machine is $10,000- $12,000.

                Dr. Adanur is responsible for fiber and fabric technology, and coating and laminating process.  Dr. Choe is an expert in fuel cells, who will test the new membrane electrode assemblies for performance increase. He will also help with automation.  Dr. Fan will concentrate on polymer chemistry and chemical analysis.  Dr. Warner, a material scientist, will deal with polymer structures and coating technology.  Two graduate students are needed for the project.

 

Activities:

 

A meeting was held between Dr. Adanur and Dr. Fan on February 16, 2004 during the National Textile Center forum in Hilton Head, SC.

 

A graduate student at Auburn Textile Engineering has bee hired to work on the project.

Manufacturers of lab scale coating systems have been contacted for the purpose of purchasing a coating system. Extended literature search is being done.

 

Graduate Student: Mr. Gunes Inan, Auburn University, Department of Textile Engineering,  Ph.D. Student

 

References:

 

  1. Bush, G. W., State of the Union address, Tuesday, January 28, 2003, Washington D. C., (www.cnn.com/2003/01/28/sotu.transcript.4/index.html, accessed August 21, 2003).
  2. Smith, E. M., “Nano Bootcamp Translates Science into Usable Technology”, American Society of Mechanical Engineers (ASME) News, Vol. 22, No. 3, March 2003.
  3. Feder, B. J., “For Far Smaller Fuel Cells, a Far Shorter Wait”, www.nytimes.com/2003/03/16/business/yourmoney/16FUEL.html (accessed March 16, 2003).
  4. Haile, S. M., “Materials for Fuel Cells”, Materials Today, March 2003, pp. 24-29.
  5. Marsh, G., “Membranes Fit for a Revolution”, Materials Today, March 2003, pp. 28-43.
  6. Jacobs, M., NTC Director, Private Communication, 22 July 2003, Auburn University, Auburn, AL.
  7. Fuel Cells: Trends in Research and Applications, Edited by A. J. Appleby and T. Beresovski, Hemisphere Pub. Corp., Washington, 1987.
  8. Fuel Cell Systems, Edited by Leo J. M. J. Blomen and M. N. Mugerwa, New York, Plenum Press, 1993.
  9. Kordesch, K., and Gunter, S., “Fuel Cells and Their Applications”, Weinheim, Germany, New York, 1996.
  10. Larminie, J., and Dicks, A., “Fuel Cell Systems Explained”, Chichester (England), New York, Wiley, 2000.
  11. Proceedings of the Symposium on Fuel Cells: Edited by R. E. White and A. J. Appleby, Nov. 6-7, 1989, San Fransisco, CA.
  12. Skinner, S. J., and Kilner, J. A., “Oxygen Ion Conductors”, Materials Today, March 2003, pp. 30-37.
  13. History of Fuel Cells in www.princeton.edu/~dcahan/fuelcells, accessed August 25, 2003.
  14. Kolbusch, T., “Coating Technologies for Fuel Cells – Energy Concepts for the Future”, Private Communication, August 2003.
  15. Sandbank, B., B.C. Technologies, Inc., Spartanburg, SC, Private Communication, August 2003.
  16. Fuel Cell Roadblocks, www.princeton.edu/~dchan/fuelcells, accessed August 25, 2003.
  17. Burgess, B., and Sandbank, B., “Machinery in Perfection, EasyFuelCellCoater for Cell Stack Components”, BC Technologies, Inc., Private Communication.
  18. New Pilot/Production Line for Fuel Cell Components Delivered by Coatema Coating Machinery GmbH, Press Release, January 2002.